Induction probe for the measurement of magnetic susceptibility

Abstract

The probe comprises two inductance windings mounted in opposition and conted to an a.c. generator, a measurement winding placed at right angles between the two inductance windings and a measurement voltage detector. A compensation winding is placed coaxially and symmetrically with the measurement winding in relation to the axis of the inductance windings, thus permitting enhanced sensitivity of the probe and a directional effect. Potential applications include continuous recording of magnetic susceptibility along a vertical borehole wall and ore sorting on a conveyor belt.

What we claim is: 
     
       1. A probe for the measurement of magnetic susceptibility of the type comprising an axis and two coaxial inductance windings for generating two magnetic inductions opposite in direction, said windings being mounted in opposition and having an axis parallel to the axis of the probe and being connected to a generator for producing alternating current at a predetermined frequency, and a measurement winding for measuring a magnetic induction between said two coaxial inductance windings, said measurement winding being placed between the two inductance windings and off-center with respect to said axis of said inductance windings, said measurement windings having an axis perpendicular to the axis of said two inductance windings, said measurement winding being connected to means for detecting a voltage at the frequency of said generator, wherein said measurement probe further comprises a compensation winding for reinforcing the induction produced in the measurement winding, said compensation winding being off-center with respect to the axis of said two coaxial inductance windings, said compensation winding being symmetrical with said measurement winding with respect to said axis of said two coaxial inductance windings. 
     
     
       2. A probe according to claim 1, wherein the compensation winding is closed on a variable resistor.